Ireland flanker Stephen Ferris has undergone surgery on an ankle injury but there has been no time frame placed on how long he is set to be out of action for.

Ferris sustained the injury against Edinburgh on November 2 and subsequently missed Ireland's autumn Test programme. With Ulster coming into a key time in their season both on the RaboDirect PRO12 and Heineken Cup front, the news that Ferris is set for a spell on the sidelines will come as a blow to the Irish province.

Ulster have not given any indication of how long Ferris is set to be out for with their statement regarding the player's injury saying: "Stephen will be reviewed in the coming weeks to establish an accurate time period for recovery and to assess when he will fit to return to play."

Ferris, who last played for Ireland back in March, said of the injury on Twitter: "Thanks for all the MSG and tweets that I have received, it's been overwhelming. Operation went well and I'm on the road to recovery."

Ireland kick off their Six Nations campaign on February 2 against Wales in Cardiff and they will be hopeful that the 27-year-old has recovered in time for that match.